Fentanyl, in particular fentanyl citrate is known as a pharmaceutical having a high analgesic effect. However, there was no useful administration method of the pharmaceutical for relatively long lasting pains such as carcinomatous pains, since its elimination half life is short and thus its effects does not last though it is utilized for the constant rate instillation before and after operation.
In the USA, a prolonged-action patch formulation containing fentanyl base (trade name: DURAGESIC) is put on the market. However, it has the disadvantage of being highly irritative to administered regions (The PII value showing a primary irritant index to rabbit skins of the patch formulation is 2.2, which is a very high value compared with that of the formulation of the present invention which is 0.3 to 0.8 (see Table 3).
Further, although the attempts to formulate fentanyl citrate into a tape formulation for percutaneous administration have been made, it could not be used clinically, since the solubility of fentanyl citrate in nonaqueous base is low and thus the transdermal permeable property of the formulation, in which fentanyl is contained in a nonaqueous base, is very low.
Therefore, an object of the present invention is to dissolve the above problems in connection with the prior arts, and to provide a tape formulation for percutaneous administration containing fentanyl, which has a low irritative property to skin, which is extremely excellent in the transdermal permeable property of fentanyl, and which is stable during the storage period.
The present inventors have researched earnestly in order to achieve the above object, and as the results, they found that a tape formulation for percutaneous administration which is extremely excellent in transderaml permeable property and which has a low irritative property to skin, can be prepared, by adding sodium acetate to a pressure sensitive adhesive base containing fentanyl or a salt thereof, and thus completed the present invention.